Gymnocarpium dryopteris (Linnaeus) Newman. Common name: Northern Oak Fern.

Triploids are known from the mountains of VA. Their identity is uncertain; based on geography they are presumably G. appalachianum × dryopteris [AAJ], but could be G. ×brittonianum (Sarvela) Pryer & Haufler [= G. disjunctum × dryopteris = AJJ]. Triploids can be distinguished by the presence of malformed spores, irregular in shape and size, often intermixed with large round spores (vs. all spores reniform and relatively uniform in size and shape).

Phenology: Jun-Sep. Habitat: Moist, rocky forests, southwards at medium to high elevations. Distribution: Circumboreal, occurring throughout northern and central Eurasia, Greenland, south in North America to MD (?), e. WV, s. PA, OH, MI, IL, IA, w. SD, CO, n. NM, c. AZ, and OR.

Origin/Endemic status: Native

Taxonomy Comments: See Pryer & Haufler (1993) for a detailed analysis of the distinguishing features of G. appalachianum and G. dryopteris. Rothfels et al. (2014) confirmed its origin as an allotetraploid derived from G. appalachianum and the w. North American/e. Asian G. disjunctum (Ruprecht) Ching. Karyotype = AAJJ.

Synonymy ⓘ: = Can, FNA2, FoC, GrPl, Il, K4, NE, NS, NY, Pa, POWO, Pryer & Haufler (1993); Polypodium dryopteris L.; = n/a — Tat; < Dryopteris disjuncta (Ledeb.) C.V.Morton — F; < Gymnocarpium dryopteris (L.) Newman — C, G, W, WV. Basionym: Polypodium dryopteris L. 1753

Links to other floras: = Gymnocarpium dryopteris - FNA2

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: UPL
• Eastern Mountains and Piedmont: UPL (taxonomic split from wetland indicator species)
• Great Plains: FACU (taxonomic split from wetland indicator species)
• Midwest: FAC (taxonomic split from wetland indicator species)
• Northcentral & Northeast: FACU (taxonomic split from wetland indicator species)

Heliophily ⓘ: 3